Question

How many moles of oxygen atoms are in 100.0 g of P2O5?

Answer 1

Molar mass of P2O5

• 2(31)+5(16)
• 62+80
• 142g/mol

Now

no of moles

• Given mass /molar mass
• 100/142
• 0.7mol

1 mol P2O5 contain 5 moles O2

0.7mol P2O5 contains 5×0.7=0.35mol O2